System and method for ultra wideband radio frequency scanning and signal generation

ABSTRACT

A system for radio transmission, arranged in a single signal chain and including a direct digital synthesis (DDS) signal generator providing a signal within a first bandwidth; a frequency multiplier in signal communication with said DDS signal generator; said frequency multiplier adapted to convert said signal within said first bandwidth to a multiplied signal within a second bandwidth, wherein said second bandwidth encompasses a wider frequency range than said first bandwidth; a processor in communication with said DDS signal generator for programming said DDS signal generator to provide said signal within said first bandwidth; said processor further adapted to reprogram said DDS signal generator to alter said first bandwidth; a radio frequency (RF) port for transmitting said signal as a wideband signal; and, a radio frequency (RF) mixer for mixing an intermediate frequency signal with said multiplied signal to generate an RF signal; said RF port transmitting said RF signal as said wideband signal.

FIELD OF THE INVENTION

The invention relates to the field of signal generation and receptionfor radio frequency (RF) communications.

BACKGROUND OF THE INVENTION

Radio frequency (RF) communications devices are ubiquitous and used inan array of varying applications. In some applications, a frequency bandis selected before a communication signal is sent to ensure nocross-over with other RF signals. In order to accomplish this, a rangeof frequencies is scanned to determine one suitable for sending thesignal, and once identified, the signal is communicated. Generally, thescanning time is negligible in comparison to the length of the signalbeing sent and is not of particular concern.

Another application is one where a wide range of frequencies needs to bescanned as quickly as possible to identify potential threats or signalsof interest, called full-band scanning. This application requiresminimal band revisit times such that the likelihood of missing shortbursts of energy is minimized. This can be accomplished in a variety ofmanners, but the manner applicable to this patent is in its widebanddata capture capability and very fast retuning capability.

In this application fractions of a second can have a direct impact onthe outcome of crucial events, the scanning time becomes an importantmetric. In addition, where security is an issue, a wide frequency rangeis also desirable. This is particularly true for military and defenseapplications such as cognitive radio, electronic warfare (signaljamming) and other military full-band spectrum scanning applications.

Examples of currently available prior art devices in the defense spacewhich attempt to resolve the high-speed tuning problem include theCHAMP-WB-DRFM produced by Curtis-Wright™ Defense Solutions, the EverestSI-9138 by DRS Technologies™, the Eclipse RXR6300 by Esterline™Corporation, the RF-7102 by Spectrum Signal Processing™, and the ExBW-Rxby Argon ST™ Inc. These prior art RF transmitting and receiving devicesin the military space are typically capable of tuning in the order of 50jps, and many cannot operate at this tuning time within a full widebandspectrum of DC—6 GHz. Some also tend to be fairly expensive and complexto produce that their integration with other devices is limited.

There is therefore a need in the art to address one or more of the aboveidentified problems with prior art devices, and in particular to providefor a signal generation device incorporating an ultra wideband radioscanning and/or generation device capable of providing one or moreadvantages over the prior art, such as one or more of improved tuningtimes, ease of manufacture, and simplicity of design leading to lowercost systems.

SUMMARY OF THE INVENTION

It is one object of the invention to alleviate at least one of theaforementioned problems with the prior art. In view of this, there isdisclosed in one embodiment of the invention a system for radio scanningincluding a direct digital synthesis (DDS) signal generator providing asignal within a first bandwidth; a frequency multiplier in signalcommunication with the DDS signal generator; the frequency multiplieradapted to convert the signal within the first bandwidth to a multipliedsignal within a second bandwidth, wherein the second bandwidthencompasses a wider frequency range than the first bandwidth; aprocessor in communication with the DDS signal generator for programmingthe DDS signal generator to provide the signal within the firstbandwidth; the processor further adapted to reprogram the DDS signalgenerator to alter the first bandwidth; and a radio frequency (RF) portfor transmitting the signal as a wideband signal.

According to one aspect of the invention, there is further provided adigital-analog converter (DAC) for receiving a digital signal to betransmitted and converting the digital signal into an analog signal; adata converter/mixer for converting the analog signal to an intermediatefrequency signal; and a radio frequency (RF) mixer for mixing theintermediate frequency signal with the multiplied signal to generate anRF signal; the RF port transmitting the RF signal as the widebandsignal.

According to another aspect of the invention, there is further providedone or more of: a bandpass filter between the DDS signal generator andthe frequency multiplier; an RF bandpass filter between the RF mixer andthe RF port; and a DAC bandpass filter between the data converter/mixerand the RF mixer.

According to another aspect of the invention, the first bandwidth is inthe range of DC to 1.6 GHz.

According to another aspect of the invention, the second bandwidth is inthe range of DC to 6 GHz.

According to another aspect of the invention, the processor is adaptedto reprogram the DDS signal generator within about 1 μs.

According to another aspect of the invention, the processor is adaptedto reprogram the DDS signal generator in less than 1 μs.

According to a second embodiment of the invention, there is provided aradio frequency (RF) port for receiving an incoming wideband signal; adirect digital synthesis (DDS) signal generator providing a signalwithin a first bandwidth; a frequency multiplier in signal communicationwith the DDS signal generator; the frequency multiplier adapted toconvert the signal within the first bandwidth to a multiplied signalwithin a second bandwidth, wherein the second bandwidth encompasses awider frequency range than the first bandwidth; a processor incommunication with the DDS signal generator for programming the DDSsignal generator to provide the signal within the first bandwidth; theprocessor further adapted to reprogram the DDS signal generator to alterthe first bandwidth; a radio frequency (RF) mixer for mixing theincoming wideband signal with the multiplied signal to generate anintermediate frequency signal; a data converter/mixer for converting theintermediate frequency signal into an intermediate frequency signal; andan analog-digital converter (ADC) for receiving the intermediatefrequency signal and converting the intermediate frequency signal into adigital signal.

According to one aspect of the second embodiment, there is furtherprovided one or more of: a bandpass filter between the DDS signalgenerator and the frequency multiplier; an RF bandpass filter betweenthe RF mixer and the RF port; and a DAC bandpass filter between the dataconverter/mixer and the RF mixer.

According to another aspect of the second embodiment, the firstbandwidth is in the range of DC to 1.6 GHz.

According to another aspect of the second embodiment, the secondbandwidth is in the range of DC to 6 GHz.

According to another aspect of the second embodiment, the processor isadapted to reprogram the DDS signal generator within about 1 μs.

According to a third embodiment of the invention, there is provided atransmit/receive switch for switching between a radio scanning system ofclaim 2 and a radio transmission system of claim 8.

According to one aspect of the third embodiment, the frequencymultiplied signal is shared between transmit and receive operations in ahalf duplex, time divisive multiplexing manner.

According to another aspect of the third embodiment, the first bandwidthis in the range of DC to 1.6 GHz.

According to another aspect of the third embodiment, the secondbandwidth is in the range of DC to 6 GHz.

According to another aspect of the third embodiment, the processor isadapted to reprogram the DDS signal generator within about 1 μs.

Other advantages, features and characteristics of the present invention,as well as methods of operation and functions of the related elements ofthe structure, and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing detailed description and the appended claims with reference tothe accompanying drawings, the latter of which is briefly describedhereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are believed to be characteristic of theaccording to the present invention, as to its structure, organization,use and method of operation, together with further objectives andadvantages thereof, will be better understood from the followingdrawings in which a presently preferred embodiment of the invention willnow be illustrated by way of example. It is expressly understood,however, that the drawings are for the purpose of illustration anddescription only, and are not intended as a definition of the limits ofthe invention. In the accompanying drawings:

FIG. 1 is a schematic drawing of an embodiment of the invention arrangedin a transmit configuration.

FIG. 2 is a schematic drawing of an embodiment of the invention arrangedin a receive configuration.

FIG. 3 is a schematic drawing of an embodiment of the invention arrangedin a transceiver configuration.

FIGS. 4 and 5 show the probability of an intercept of a fast revisittime as provided by the invention when compared to the prior art.

FIG. 6 illustrates the ability of the invention to target multiple bandsin a much shorter timeframe as compared to the prior art.

DETAILED DESCRIPTION

The need for the present invention arises in part due to a desire toprovide near-instantaneous bandwidth reception, scanning, and/or signalgeneration for radio frequency (RF) communications over a wide operatingrange. Requirements for operation over a wide range of RF bandwidths areincreasing due to demands from applications such as cognitive radio,electronic warfare and spectrum monitoring. The cognitive radioapplication has enhanced requirements which dictate that signalreception and generation will have the capability of being relocated todifferent radio bands within short periods of time. A radio with thecapability of generating and receiving signals over a wide bandwidth andmoving almost instantaneously between bands is of significant value tothis application. These ultra wide bandwidth receivers and generatorsalso have applications in electronic attack (e.g. responsive signaljamming), signal and interference detection and hunting and signaldemodulation, classification and fingerprinting. The invention may beimplemented as a combination of hardware and/or software and ispreferably provided on a circuit board provided on a card which canreadily be integrated into RF communications devices. Such details ofintegration are peripheral to the invention and thus are not describedin further detail.

Adaptations of the invention permit operation as a transmitter, areceiver or as a transceiver providing flexibility to a wide array ofpotential applications. The preferred operating parameters, and indeedthose enabled by the structure described below, provides for operationover a wide frequency range, typically DC to 6 GHz. However, it will beappreciated that adjustments may readily be made to cover a wider ormore narrow operating range as dictated by specific applications.

In general, the system operates by providing a direct digital synthesis(DDS) signal generation engine to generate a digital signal. The DDSgeneration engine can be reprogrammed to operate within particularoperating ranges in a relatively short period of time. In the systemdisclosed herein, this reprogramming to move the operating range occursin about 1 μs, and is limited in part by the physical link to the DDSgeneration engine. Improvements in materials or otherwise with respectto the physical digital link may lead to even faster reprogrammingtimes. Current state-of-the-art DDS generation engines have a limitedoperating range, such as DC to 1.6 GHz, such that in practice the systemsteers the signal generated by the DDS generation engine to a widebandoperating range, such as DC to 6 HGz, which covers the entire intendedoperating range target. This may be accomplished through frequencymultiplication. The frequency multiplied signal can be mixed with asignal from a data converter (i.e. a digital-analog or an analog-digitalconverter) if so desired

Transmit Configuration

Referring now to FIG. 1, there is shown one embodiment of the inventionin which the system is adapted to operate as a transmitter of RFcommunications. The system 10 includes a direct digital synthesis (DDS)signal generation engine 20 in communication with a frequency multiplier30. The frequency multiplier 30 is adapted to convert the signal fromthe DDS generation engine, which has a limited operating range asmentioned above, into an ultra wideband operating range such as DC to 6GHz.

The circuitry of FIG. 1 may be mated to a DAC for the purposes ofarbitrary waveform generation. A potentially good match to the inventiondescribed within is to use an ultra wideband DAC to allow for ultrawideband signal generation in addition to the fast band relocationprovided by the DDS and multipliers. A digital to analog converter (DAC)90 generates a baseband signal, which is then modulated and/orupconverted by modulator/converter 100 to an intermediate frequencyprior to being mixed with the frequency multiplied signal by the RFmixer 40 to generate the output RF signal via RF port 70. Optionally,the DAC signal may be modulated and/or mixed at baseband (IF=0 Hz) andthus avoid upconversion of the DAC signal to the intermediate frequency.It is also contemplated that the DAC may be used to generate a signaldirectly at the intermediate frequency by using the signal generated bythe DAC outside of the first Nyquist zone. This technique is oftenreferred to as undersampling, harmonic sampling, bandpass sampling orintermediate frequency sampling.

A processing unit (not shown) may be connected to either or both of theDAC and the DDS to generate a signal to be transmitted and control thereprogramming of the DAC, respectively.

A number of filters 50, 60, 110 may be associated with either the DDSsignal generator 20, the output signal from the converter/mixer 100 orthe signal resulting from the mixer 40. These filters are generallyknown in the art and are selected depending on requirements for signalchain noise, spurs and image rejection, for example.

In operation, the output frequency band of the DDS 20 is bandpassfiltered by the filter 50 before it is frequency multiplied to achieve abroader frequency coverage at RF bands. This broader frequency coverageenables the wideband objectives of the present invention, whilepermitting tuning times corresponding with the narrow range at the DDS.Accordingly, reprogramming the DDS within its narrower range becomes thetime limiting factor, while the outcome of wideband scanning is stillachieved after the signal is frequency multiplied. Once the frequencymultiplied signal is mixed with the data signal from the DAC, a complexsignal is generated that may be transmitted as required. As discussedabove, the DAC may generate signals in a variety of ways which may beknow in the art, prior to being mixed by the RF mixer 40 with thefrequency multiplied signal from the DDS 20.

Receive Configuration

Referring now to FIG. 2, there is shown an embodiment of the inventionadapted to performing ultra wideband signal capture. The system 200 ofFIG. 2 makes use of the same general concept as that of FIG. 1, whereina signal from DDS 210 is frequency multiplied by multiplier 220 in orderto widen the frequency band being scanned. In this configuration,reception of signals from a wideband range is made possible along withtuning times in the wideband frequency inline with those mentionedabove.

An input signal is received at RF port 240, optionally bandpass filteredby filter 290, before being mixed by RF mixer 230 with the frequencymultiplied DDS signal. The DDS signal is generated by DDS 210 andoptionally bandpass filtered by filter 295 before being frequencymultiplied by frequency multiplier 220. The output signal from the RFmixer is preferably an intermediate frequency (IF) signal. The IF signalis then mixed by the data converter/mixer 260 to generate a basebandsignal that is sampled by the analog to digital converter (ADC). In onevariant, it is possible to sample the IF signal directly by the ADCusing a second or subsequent Nyquist zone. The system 200 has thecapability of being mated to an ADC for the purposes of performing ultrawideband signal capture. A potentially good match to the inventiondescribed within is to use an ultra wideband ADC to allow for ultrawideband signal reception in addition to the fast band relocationprovided by the DDS and multipliers

Other than being configured to receive signals, the functioning andadvantages of the embodiment illustrated in FIG. 2 are analogous tothose as were described with respect to FIG. 1.

Transceiver Configuration

FIG. 3 shows a third embodiment of the invention in which the system 300is arranged in a transceiver configuration. Similarly to the previoustwo embodiments, DDS 310 generates a signal within a limited bandwidth,which is then frequency multiplied by multiplier 320. An optional filter300 is used to bandpass filter the signal leaving the DDS 310. Thefrequency multiplied signal is then mixed at an RF mixer 360, witheither a received signal or a transmitted signal, depending upon themode in which the transceiver is operating. The frequency multipliedsignal is effectively shared between transmit and receive operations ina half-duplex, time divisive multiplexing fashion. The position ofswitch 370 dictates which operation is occurring at a particular time.

In the transmit mode, DAC 400, data converter/mixer 390 and filter 380function as was described with similarly named elements in FIG. 1. Inthe receive mode, ADC 450, data converter/mixer 440 and filter 420function as was described with respect to similarly named elements inFIG. 2.

The Direct Digital Synthesis Signal Generator

A suitable DDS is chosen for use in this invention with wide bandwidthand a high-speed, low latency link allowing retuning of the DDS across awide frequency range to occur in a short period of time. It is possibleto purchase state-of-the art DDS devices capable of this type ofoperation from vendors or to create a DDS using a combination of a fieldprogrammable gate array (FPGA) or application-specific integratedcircuit (ASIC) and a high-speed digital-to-analog converter (DAC).

Examples

FIGS. 4, 5 and 6 show test results of a system as herein describedversus that of a prior art system. FIG. 4 shows three different signalsof interest, and the benefits of a fast revisit time as provided by theinvention. The top chart in FIG. 4 shows the system of the invention inone full cycle having an automatic gain control time of approximately 2μs, an available capture time in the order of 400 ns, and a return andsetup time of less than 1 As to modify the seek frequency. As shown,each of the three signals of interest having a relatively short durationof 11 μs are detected at the appropriate frequency at either C₁, C₂, orC₃. This is a direct result of having minimized the return and set-uptime for scanning the next frequency. The chart at the bottom of FIG. 4shows a prior art system having a return and set-up time ofapproximately 50 μs. As shown, only one of the signals of interest aredetected by the prior art system. The signals of interest shown are eachat a particular, and different bandwidth. As will also be evident,switching bands in the prior art system takes a significantly longertime and runs the credible risk of missing a signal of interestaltogether, particularly in military and defense applications asdiscussed above where these differences can be critical.

FIG. 5 show another comparison in which the automatic gain control hasbeen omitted, allowing for even lower cycle times, and permitting fortwo captures on each signal of interest when compared to the results inFIG. 4. It is possible to operate without automatic gain control byeither restricting the dynamic operating range or by performing gaincontrol using the captured data instead of a separate control loop, forexample. Again, the prior art system is incapable of detecting more thanone signal of interest, even with the gain control removed.

FIG. 6 shows that for applications such as electronic attack it ispossible to target multiple bands (i.e. requires retuning) in a muchshorter timeframe. With a short signal (may be a sweep, spot orarbitrary waveform signal) of 5 us a system employing the invention canmove quickly between bands using the disclosed transmitter architecture.For a longer retuning time it becomes impractical to attack multiplefrequency bands since the retuning time eclipses the time on target.This is shown in the state-of-the-art signal generator scenario whereswitching bands takes much longer than the time on target. Prior artsystems would need to use multiple transmitters, thus increasing cost toalleviate their shortcomings.

The invention is also applicable to the area of signal generation acrossa single wide frequency range or multiple frequency ranges. Inparticular the ability to task a single signal generation source toaddress multiple bands very quickly allows for cost reduction through areduction of multiple signal generators down to one. This can greatlyreduce system costs not just in the signal generator itself but inconnected power amplifiers, switches, diplexors and antennas. Theserapid signal generation sources can also be used for cognitive radioallowing for relocation of the signal source across a wide range offrequencies exceeding that offered by the bandwidth of the digital toanalog converter (DAC).

Other modifications and alterations may be used in the design andmanufacture of other embodiments according to the present inventionwithout departing from the spirit and scope of the invention, which islimited only by the accompanying claims.

1. A system for radio transmission comprising: a direct digitalsynthesis (DDS) signal generator providing a signal within a firstbandwidth; a frequency multiplier in signal communication with said DDSsignal generator; said frequency multiplier adapted to convert saidsignal within said first bandwidth to a multiplied signal within asecond bandwidth, wherein said second bandwidth encompasses a widerfrequency range than said first bandwidth; a processor in communicationwith said DDS signal generator for programming said DDS signal generatorto provide said signal within said first bandwidth; said processorfurther adapted to reprogram said DDS signal generator to alter saidfirst bandwidth; a radio frequency (RF) port for transmitting saidsignal as a wideband signal; and, a radio frequency (RF) mixer formixing an intermediate frequency signal with said multiplied signal togenerate an RF signal; said RF port transmitting said RF signal as saidwideband signal; wherein the system is arranged in a single signalchain.
 2. The system according to claim 1, further comprising: adigital-analog converter (DAC) for receiving a digital signal to betransmitted and converting said digital signal into an analog signal;and, a data converter/mixer for converting said analog signal to saidintermediate frequency signal.
 3. The system according to claim 2,further comprising one or more of: a bandpass filter between said DDSsignal generator and said frequency multiplier; an RF bandpass filterbetween said RF mixer and said RF port; and a DAC bandpass filterbetween said data converter/mixer and said RF mixer.
 4. The systemaccording to claim 1, wherein said first bandwidth is in the range of DCto 1.6 GHz.
 5. The system according to claim 4, wherein said secondbandwidth is in the range of DC to 6 GHz.
 6. The system according toclaim 5, wherein said processor is adapted to reprogram said DDS signalgenerator in less than 1 μs.
 7. A system for radio scanning comprising:a radio frequency (RF) port for receiving an incoming wideband signal; adirect digital synthesis (DDS) signal generator providing a signalwithin a first bandwidth; a frequency multiplier in signal communicationwith said DDS signal generator; said frequency multiplier adapted toconvert said signal within said first bandwidth to a multiplied signalwithin a second bandwidth, wherein said second bandwidth encompasses awider frequency range than said first bandwidth; a processor incommunication with said DDS signal generator for programming said DDSsignal generator to provide said signal within said first bandwidth;said processor further adapted to reprogram said DDS signal generator toalter said first bandwidth; a radio frequency (RF) mixer for mixing saidincoming wideband signal with said multiplied signal to generate anintermediate frequency signal; a data converter/mixer for convertingsaid intermediate frequency signal into a baseband frequency signal;and, an analog-digital converter (ADC) for receiving said basebandfrequency signal and converting said baseband frequency signal into adigital signal; wherein the system is arranged in a single signal chain.8. The system according to claim 8, further comprising one or more of: abandpass filter between said DDS signal generator and said frequencymultiplier; and, an RF bandpass filter between said RF mixer and said RFport; and a DAC bandpass filter between said data converter/mixer andsaid RF mixer.
 9. The system according to claim 8, wherein said firstbandwidth is in the range of DC to 1.6 GHz.
 10. The system according toclaim 8, wherein said second bandwidth is in the range of DC to 6 GHz.